1. Field of the Invention
The present invention relates to a photodiode array and an image pickup device and, in particular, a photodiode array having photosensitivity at the long-wavelength side including the near infrared region and an image pickup device using the photodiode array.
2. Description of the Related Art
Group III-V compound-based semiconductors have recently been drawing attention as compound semiconductors having a band gap energy corresponding to the near infrared region or a region of longer wavelengths, and thus research and development thereof is underway. An example of a disclosed application of such a compound is a night-vision camera that receives natural light at night by means of a photodiode array constituted of photodiodes having an InGaAs-based absorption layer that undergoes lattice matching with an InP substrate and that is arranged on the InP substrate (see Marshall J. Cohen and Gregory H. Olsen “Near-IR imaging cameras operate at room temperature,” LASER FOCUS WORLD, June 1993, pp. 109-113). Such a night-vision camera allows for image pickup under natural light without artificial lighting regardless of whether it is dark or rainy.
Such night-vision cameras, however, cannot provide clear images. This is because a two-dimensional photodiode array receiving incident light coming from the plane of incidence, the back surface of the InP substrate, experiences optical crosstalk occurring between adjacent photodiodes; this optical crosstalk reduces effective resolution, thereby resulting in blurred images.